Search for New Function of RNAs

本小组的目标是：(1)通过发现新的RNA分子并阐明其功能来了解RNA功能的变化；(2)通过分析tRNA和rRNA的功能结构来发现它们的新功能。如下图所示，我们几乎达到了我们的目标。(1)寻找新的小RNA分子：从细菌中发现了许多新的小RNA分子，如支原体、大肠杆菌和枯草芽孢杆菌，动物细胞及其结构也被确定。此外，对功能感兴趣的分子进行了功能结构分析。特别是10Sa RNA至少存在于所有真细菌中，作为mRNA通过反翻译的机制在未完成的多肽上添加标记片段。此外，对一个携带和不携带10Sa RNA的ts突变体的分析表明，该RNA在细胞中具有其他多种功能。许多其他小RNA包括MCS4 RNA，4.5S RNA已被发现，其功能正在分析中。(2) tRNA和rRNA的新功能：通过突变体分析确定了大肠杆菌中所有tRNA被氨基酰基-tRNA合成酶识别的结构，并将相同的分析应用于酵母系统。这些分析结果为tRNA的进化、tRNA的识别、歧视的起源提供了重要的建议。同时，对大肠杆菌23S rRNA的硫链结构域（GTP酶中心）和毒素结构域的分析表明，在核糖体上GTP水解反应过程中，这些结构域改变了它们的构象，通过串扰相互作用。此外，已发现线粒体大rRNA在极细胞形成中起作用。

The goal of this groups is (1) to know the variation of RNA functions by finding new RNA molecules and elucidating their functions and (2) to find out the new functions of tRNA and rRNA by analysis of their functional structures. As shown below, we have almost reached to our goal.(1) Search for new small RNA molecules : A number of new small RNA molecules have been found from bacteria, such as Mycoplasma, Escherichia coli and Bacillus Subtilis, and animal cells and their structures have also been determined. Furthermore, for functionally interesting molecules, their functional structures have been analyzed. Especially, 10Sa RNA has been found to exist at least in all eubacteria, working as an mRNA to add a tag gragment to the uncompleted polypeptide by the mechanism of trans-translation. Moreover, the analysis fo a ts-mutant that shows different growth with and without 10Sa RNA suggested that this RNA has other various functions in the cell. Many other small RNAs including MCS4 RNA,4.5S RNAH has been found and their functions are being analyzed.(2) New functions of tRNA and rRNA : the recognized structures of all the tRNA in the Escherichia coli by aminoacyl-tRNA synthetase have been determined by the mutant analysis and the same analysis has been applied to the yeast system. The results obtained by these analysis gave important suggestions for evolution of tRNA and recognition of tRNA,origin of the discrimination. In parallel, the analysis of the thiostrepton domain (GTPase center) and the Toxin domain of Escherichia coli 23S rRNA showed that during the GTP hydrolysis reaction on ribosome these domains change their conformations, interacting with each other by the cross talk. Furthermore, the mitocondrial large rRNA has been found to function in pole cell formation.